138 Memoirs of the Indian Museum. [Vol. V, 1915.] 



Suborder OPERCULATA. 



Family Ba^anidae. 



Balanus amphitrite, Darwin. 



1854. Balanus amphitrite, Darwin, Mon. Cirripedia, Balanidae, p. 240, pi. v, figs. 2«-2c. 



All our specimens from the Chilka Lake belong to Darwin's var. communis, but 

 they vary considerably in shape, some being much more depressed than others. The 

 largest have a diameter of about 15 mm. 



The species is abundant on oyster-shells, fish-traps and wooden posts in the outer 

 channel of the Chilka Lake and occurs singly or in small numbers on the shells of 

 Potamides and other Gastropods and Lamellibranchs. In the main area a few soli- 

 tary living individuals of small size were observed on rocks, mostly towards the end 

 of the dry season, while a relatively large number of dead shells were observed in the 

 same situation. On one occasion in the season of low salinity the bottom of a boat 

 in Rambha Bay was found to be covered with small living individuals, but it had 

 possibly arrived recently from the outer division of the lake-system. In the outer 

 channel the specific gravity of the water in which apparently healthy barnacles were 

 observed varied from 1000 to 1-0265. I have seen them in brackish or almost fresh 

 water in the Gangetic delta, near Madras and in Cochin on the west coast of India. The 

 species is common in all the warmer seas and is carried into those of the northern 

 temperate zone on the bottom of ships. In the Bay of Bengal it is perhaps the 

 commonest of the littoral Operculata. 



Larval Balani, probably of this species, were abundant in our tow-nettings taken 

 in the outer channel in March. This is also the case in collections made in the 

 same month in the shallower parts of the Bay of Bengal. 



B. amphitrite is remarkable for the rapidity of its growth and for its power of 

 resisting unfavourable circumstances. Professor Herdman l found specimens of a 

 diameter of 8 mm. on baskets that had been in the sea off Ceylon for 21 days. 

 I have little doubt that the species breeds regularly in the outer channel of the 

 Chilka Lake and that stray larvae are carried into the main area and occasionally 

 find it possible to settle down and undergo their metamorphosis, without being able 

 to survive it for more than a few months. 



The vicissitudes undergone annually by barnacles attached to oyster-shells in the 

 outer channel are sufficient proof of the strong vitality of the species, but even more 

 remarkable evidence is afforded by the fate of those individuals that attach them- 

 selves to prawn-traps in the neighbourhood of Satpara. The traps are placed in the 

 lake in the evening and, remaining in the water all night, are removed at dawn. 

 Throughout the heat of the day they lie on the shore, fully exposed to the sun's 

 rays. Nevertheless, the barnacles on them survive. We saw many instances of 

 this, more particularly in September, 1913, and in the same month of 1914. Speci- 

 mens from such situations are small (not exceeding 9 mm. in diameter) and dull in 

 colour, but otherwise apparently normal. 



1 Ceylon Pearl Fisheries V, p. 147 (1906). The dates were April 17th to May 9th. 



